// SPDX-License-Identifier: GPL-2.0
/*
* This file contains functions which emulate a local clock-event
* device via a broadcast event source.
*
* Copyright(C) 2005-2006, Thomas Gleixner <[email protected]>
* Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
* Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
*/
#include <linux/cpu.h>
#include <linux/err.h>
#include <linux/hrtimer.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/module.h>
#include "tick-internal.h"
/*
* Broadcast support for broken x86 hardware, where the local apic
* timer stops in C3 state.
*/
static struct tick_device tick_broadcast_device;
static cpumask_var_t tick_broadcast_mask __cpumask_var_read_mostly;
static cpumask_var_t tick_broadcast_on __cpumask_var_read_mostly;
static cpumask_var_t tmpmask __cpumask_var_read_mostly;
static int tick_broadcast_forced;
static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
#ifdef CONFIG_TICK_ONESHOT
static DEFINE_PER_CPU(struct clock_event_device *, tick_oneshot_wakeup_device);
static void tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic);
static void tick_broadcast_clear_oneshot(int cpu);
static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);
# ifdef CONFIG_HOTPLUG_CPU
static void tick_broadcast_oneshot_offline(unsigned int cpu);
# endif
#else
static inline void
tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic) { BUG(); }
static inline void tick_broadcast_clear_oneshot(int cpu) { }
static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
# ifdef CONFIG_HOTPLUG_CPU
static inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }
# endif
#endif
/*
* Debugging: see timer_list.c
*/
struct tick_device *tick_get_broadcast_device(void)
{
return &tick_broadcast_device;
}
struct cpumask *tick_get_broadcast_mask(void)
{
return tick_broadcast_mask;
}
static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu);
const struct clock_event_device *tick_get_wakeup_device(int cpu)
{
return tick_get_oneshot_wakeup_device(cpu);
}
/*
* Start the device in periodic mode
*/
static void tick_broadcast_start_periodic(struct clock_event_device *bc)
{
if (bc)
tick_setup_periodic(bc, 1);
}
/*
* Check, if the device can be utilized as broadcast device:
*/
static bool tick_check_broadcast_device(struct clock_event_device *curdev,
struct clock_event_device *newdev)
{
if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
(newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
(newdev->features & CLOCK_EVT_FEAT_C3STOP))
return false;
if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
!(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
return false;
return !curdev || newdev->rating > curdev->rating;
}
#ifdef CONFIG_TICK_ONESHOT
static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
{
return per_cpu(tick_oneshot_wakeup_device, cpu);
}
static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
{
/*
* If we woke up early and the tick was reprogrammed in the
* meantime then this may be spurious but harmless.
*/
tick_receive_broadcast();
}
static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
int cpu)
{
struct clock_event_device *curdev = tick_get_oneshot_wakeup_device(cpu);
if (!newdev)
goto set_device;
if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
(newdev->features & CLOCK_EVT_FEAT_C3STOP))
return false;
if (!(newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
!(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
return false;
if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
return false;
if (curdev && newdev->rating <= curdev->rating)
return false;
if (!try_module_get(newdev->owner))
return false;
newdev->event_handler = tick_oneshot_wakeup_handler;
set_device:
clockevents_exchange_device(curdev, newdev);
per_cpu(tick_oneshot_wakeup_device, cpu) = newdev;
return true;
}
#else
static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
{
return NULL;
}
static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
int cpu)
{
return false;
}
#endif
/*
* Conditionally install/replace broadcast device
*/
void tick_install_broadcast_device(struct clock_event_device *dev, int cpu)
{
struct clock_event_device *cur = tick_broadcast_device.evtdev;
if (tick_set_oneshot_wakeup_device(dev, cpu))
return;
if (!tick_check_broadcast_device(cur, dev))
return;
if (!try_module_get(dev->owner))
return;
clockevents_exchange_device(cur, dev);
if (cur)
cur->event_handler = clockevents_handle_noop;
tick_broadcast_device.evtdev = dev;
if (!cpumask_empty(tick_broadcast_mask))
tick_broadcast_start_periodic(dev);
if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
return;
/*
* If the system already runs in oneshot mode, switch the newly
* registered broadcast device to oneshot mode explicitly.
*/
if (tick_broadcast_oneshot_active()) {
tick_broadcast_switch_to_oneshot();
return;
}
/*
* Inform all cpus about this. We might be in a situation
* where we did not switch to oneshot mode because the per cpu
* devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
* of a oneshot capable broadcast device. Without that
* notification the systems stays stuck in periodic mode
* forever.
*/
tick_clock_notify();
}
/*
* Check, if the device is the broadcast device
*/
int tick_is_broadcast_device(struct clock_event_device *dev)
{
return (dev && tick_broadcast_device.evtdev == dev);
}
int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
{
int ret = -ENODEV;
if (tick_is_broadcast_device(dev)) {
raw_spin_lock(&tick_broadcast_lock);
ret = __clockevents_update_freq(dev, freq);
raw_spin_unlock(&tick_broadcast_lock);
}
return ret;
}
static void err_broadcast(const struct cpumask *mask)
{
pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
}
static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
{
if (!dev->broadcast)
dev->broadcast = tick_broadcast;
if (!dev->broadcast) {
pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
dev->name);
dev->broadcast = err_broadcast;
}
}
/*
* Check, if the device is dysfunctional and a placeholder, which
* needs to be handled by the broadcast device.
*/
int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
{
struct clock_event_device *bc = tick_broadcast_device.evtdev;
unsigned long flags;
int ret = 0;
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
/*
* Devices might be registered with both periodic and oneshot
* mode disabled. This signals, that the device needs to be
* operated from the broadcast device and is a placeholder for
* the cpu local device.
*/
if (!tick_device_is_functional(dev)) {
dev->event_handler = tick_handle_periodic;
tick_device_setup_broadcast_func(dev);
cpumask_set_cpu(cpu, tick_broadcast_mask);
if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
tick_broadcast_start_periodic(bc);
else
tick_broadcast_setup_oneshot(bc, false);
ret = 1;
} else {
/*
* Clear the broadcast bit for this cpu if the
* device is not power state affected.
*/
if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
cpumask_clear_cpu(cpu, tick_broadcast_mask);
else
tick_device_setup_broadcast_func(dev);
/*
* Clear the broadcast bit if the CPU is not in
* periodic broadcast on state.
*/
if (!cpumask_test_cpu(cpu, tick_broadcast_on))
cpumask_clear_cpu(cpu, tick_broadcast_mask);
switch (tick_broadcast_device.mode) {
case TICKDEV_MODE_ONESHOT:
/*
* If the system is in oneshot mode we can
* unconditionally clear the oneshot mask bit,
* because the CPU is running and therefore
* not in an idle state which causes the power
* state affected device to stop. Let the
* caller initialize the device.
*/
tick_broadcast_clear_oneshot(cpu);
ret = 0;
break;
case TICKDEV_MODE_PERIODIC:
/*
* If the system is in periodic mode, check
* whether the broadcast device can be
* switched off now.
*/
if (cpumask_empty(tick_broadcast_mask) && bc)
clockevents_shutdown(bc);
/*
* If we kept the cpu in the broadcast mask,
* tell the caller to leave the per cpu device
* in shutdown state. The periodic interrupt
* is delivered by the broadcast device, if
* the broadcast device exists and is not
* hrtimer based.
*/
if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
break;
default:
break;
}
}
raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
return ret;
}
int tick_receive_broadcast(void)
{
struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
struct clock_event_device *evt = td->evtdev;
if (!evt)
return -ENODEV;
if (!evt->event_handler)
return -EINVAL;
evt->event_handler(evt);
return 0;
}
/*
* Broadcast the event to the cpus, which are set in the mask (mangled).
*/
static bool tick_do_broadcast(struct cpumask *mask)
{
int cpu = smp_processor_id();
struct tick_device *td;
bool local = false;
/*
* Check, if the current cpu is in the mask
*/
if (cpumask_test_cpu(cpu, mask)) {
struct clock_event_device *bc = tick_broadcast_device.evtdev;
cpumask_clear_cpu(cpu, mask);
/*
* We only run the local handler, if the broadcast
* device is not hrtimer based. Otherwise we run into
* a hrtimer recursion.
*
* local timer_interrupt()
* local_handler()
* expire_hrtimers()
* bc_handler()
* local_handler()
* expire_hrtimers()
*/
local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);
}
if (!cpumask_empty(mask)) {
/*
* It might be necessary to actually check whether the devices
* have different broadcast functions. For now, just use the
* one of the first device. This works as long as we have this
* misfeature only on x86 (lapic)
*/
td = &per_cpu(tick_cpu_device, cpumask_first(mask));
td->evtdev->broadcast(mask);
}
return local;
}
/*
* Periodic broadcast:
* - invoke the broadcast handlers
*/
static bool tick_do_periodic_broadcast(void)
{
cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
return tick_do_broadcast(tmpmask);
}
/*
* Event handler for periodic broadcast ticks
*/
static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
{
struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
bool bc_local;
raw_spin_lock(&tick_broadcast_lock);
/* Handle spurious interrupts gracefully */
if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) {
raw_spin_unlock(&tick_broadcast_lock);
return;
}
bc_local = tick_do_periodic_broadcast();
if (clockevent_state_oneshot(dev)) {
ktime_t next = ktime_add_ns(dev->next_event, TICK_NSEC);
clockevents_program_event(dev, next, true);
}
raw_spin_unlock(&tick_broadcast_lock);
/*
* We run the handler of the local cpu after dropping
* tick_broadcast_lock because the handler might deadlock when
* trying to switch to oneshot mode.
*/
if (bc_local)
td->evtdev->event_handler(td->evtdev);
}
/**
* tick_broadcast_control - Enable/disable or force broadcast mode
* @mode: The selected broadcast mode
*
* Called when the system enters a state where affected tick devices
* might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
*/
void tick_broadcast_control(enum tick_broadcast_mode mode)
{
struct clock_event_device *bc, *dev;
struct tick_device *td;
int cpu, bc_stopped;
unsigned long flags;
/* Protects also the local clockevent device. */
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
td = this_cpu_ptr(&tick_cpu_device);
dev = td->evtdev;
/*
* Is the device not affected by the powerstate ?
*/
if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
goto out;
if (!tick_device_is_functional(dev))
goto out;
cpu = smp_processor_id();
bc = tick_broadcast_device.evtdev;
bc_stopped = cpumask_empty(tick_broadcast_mask);
switch (mode) {
case TICK_BROADCAST_FORCE:
tick_broadcast_forced = 1;
fallthrough;
case TICK_BROADCAST_ON:
cpumask_set_cpu(cpu, tick_broadcast_on);
if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
/*
* Only shutdown the cpu local device, if:
*
* - the broadcast device exists
* - the broadcast device is not a hrtimer based one
* - the broadcast device is in periodic mode to
* avoid a hiccup during switch to oneshot mode
*/
if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
clockevents_shutdown(dev);
}
break;
case TICK_BROADCAST_OFF:
if (tick_broadcast_forced)
break;
cpumask_clear_cpu(cpu, tick_broadcast_on);
if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
if (tick_broadcast_device.mode ==
TICKDEV_MODE_PERIODIC)
tick_setup_periodic(dev, 0);
}
break;
}
if (bc) {
if (cpumask_empty(tick_broadcast_mask)) {
if (!bc_stopped)
clockevents_shutdown(bc);
} else if (bc_stopped) {
if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
tick_broadcast_start_periodic(bc);
else
tick_broadcast_setup_oneshot(bc, false);
}
}
out:
raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}
EXPORT_SYMBOL_GPL(tick_broadcast_control);
/*
* Set the periodic handler depending on broadcast on/off
*/
void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
{
if (!broadcast)
dev->event_handler = tick_handle_periodic;
else
dev->event_handler = tick_handle_periodic_broadcast;
}
#ifdef CONFIG_HOTPLUG_CPU
static void tick_shutdown_broadcast(void)
{
struct clock_event_device *bc = tick_broadcast_device.evtdev;
if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
if (bc && cpumask_empty(tick_broadcast_mask))
clockevents_shutdown(bc);
}
}
/*
* Remove a CPU from broadcasting
*/
void tick_broadcast_offline(unsigned int cpu)
{
raw_spin_lock(&tick_broadcast_lock);
cpumask_clear_cpu(cpu, tick_broadcast_mask);
cpumask_clear_cpu(cpu, tick_broadcast_on);
tick_broadcast_oneshot_offline(cpu);
tick_shutdown_broadcast();
raw_spin_unlock(&tick_broadcast_lock);
}
#endif
void tick_suspend_broadcast(void)
{
struct clock_event_device *bc;
unsigned long flags;
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
bc = tick_broadcast_device.evtdev;
if (bc)
clockevents_shutdown(bc);
raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}
/*
* This is called from tick_resume_local() on a resuming CPU. That's
* called from the core resume function, tick_unfreeze() and the magic XEN
* resume hackery.
*
* In none of these cases the broadcast device mode can change and the
* bit of the resuming CPU in the broadcast mask is safe as well.
*/
bool tick_resume_check_broadcast(void)
{
if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
return false;
else
return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
}
void tick_resume_broadcast(void)
{
struct clock_event_device *bc;
unsigned long flags;
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
bc = tick_broadcast_device.evtdev;
if (bc) {
clockevents_tick_resume(bc);
switch (tick_broadcast_device.mode) {
case TICKDEV_MODE_PERIODIC:
if (!cpumask_empty(tick_broadcast_mask))
tick_broadcast_start_periodic(bc);
break;
case TICKDEV_MODE_ONESHOT:
if (!cpumask_empty(tick_broadcast_mask))
tick_resume_broadcast_oneshot(bc);
break;
}
}
raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}
#ifdef CONFIG_TICK_ONESHOT
static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly;
static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly;
static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly;
/*
* Exposed for debugging: see timer_list.c
*/
struct cpumask *tick_get_broadcast_oneshot_mask(void)
{
return tick_broadcast_oneshot_mask;
}
/*
* Called before going idle with interrupts disabled. Checks whether a
* broadcast event from the other core is about to happen. We detected
* that in tick_broadcast_oneshot_control(). The callsite can use this
* to avoid a deep idle transition as we are about to get the
* broadcast IPI right away.
*/
noinstr int tick_check_broadcast_expired(void)
{
#ifdef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
return arch_test_bit(smp_processor_id(), cpumask_bits(tick_broadcast_force_mask));
#else
return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
#endif
}
/*
* Set broadcast interrupt affinity
*/
static void tick_broadcast_set_affinity(struct clock_event_device *bc,
const struct cpumask *cpumask)
{
if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
return;
if (cpumask_equal(bc->cpumask, cpumask))
return;
bc->cpumask = cpumask;
irq_set_affinity(bc->irq, bc->cpumask);
}
static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
ktime_t expires)
{
if (!clockevent_state_oneshot(bc))
clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
clockevents_program_event(bc, expires, 1);
tick_broadcast_set_affinity(bc, cpumask_of(cpu));
}
static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)
{
clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
}
/*
* Called from irq_enter() when idle was interrupted to reenable the
* per cpu device.
*/
void tick_check_oneshot_broadcast_this_cpu(void)
{
if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
/*
* We might be in the middle of switching over from
* periodic to oneshot. If the CPU has not yet
* switched over, leave the device alone.
*/
if (td->mode == TICKDEV_MODE_ONESHOT) {
clockevents_switch_state(td->evtdev,
CLOCK_EVT_STATE_ONESHOT);
}
}
}
/*
* Handle oneshot mode broadcasting
*/
static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
{
struct tick_device *td;
ktime_t now, next_event;
int cpu, next_cpu = 0;
bool bc_local;
raw_spin_lock(&tick_broadcast_lock);
dev->next_event = KTIME_MAX;
next_event = KTIME_MAX;
cpumask_clear(tmpmask);
now = ktime_get();
/* Find all expired events */
for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
/*
* Required for !SMP because for_each_cpu() reports
* unconditionally CPU0 as set on UP kernels.
*/
if (!IS_ENABLED(CONFIG_SMP) &&
cpumask_empty(tick_broadcast_oneshot_mask))
break;
td = &per_cpu(tick_cpu_device, cpu);
if (td->evtdev->next_event <= now) {
cpumask_set_cpu(cpu, tmpmask);
/*
* Mark the remote cpu in the pending mask, so
* it can avoid reprogramming the cpu local
* timer in tick_broadcast_oneshot_control().
*/
cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
} else if (td->evtdev->next_event < next_event) {
next_event = td->evtdev->next_event;
next_cpu = cpu;
}
}
/*
* Remove the current cpu from the pending mask. The event is
* delivered immediately in tick_do_broadcast() !
*/
cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
/* Take care of enforced broadcast requests */
cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
cpumask_clear(tick_broadcast_force_mask);
/*
* Sanity check. Catch the case where we try to broadcast to
* offline cpus.
*/
if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
cpumask_and(tmpmask, tmpmask, cpu_online_mask);
/*
* Wakeup the cpus which have an expired event.
*/
bc_local = tick_do_broadcast(tmpmask);
/*
* Two reasons for reprogram:
*
* - The global event did not expire any CPU local
* events. This happens in dyntick mode, as the maximum PIT
* delta is quite small.
*
* - There are pending events on sleeping CPUs which were not
* in the event mask
*/
if (next_event != KTIME_MAX)
tick_broadcast_set_event(dev, next_cpu, next_event);
raw_spin_unlock(&tick_broadcast_lock);
if (bc_local) {
td = this_cpu_ptr(&tick_cpu_device);
td->evtdev->event_handler(td->evtdev);
}
}
static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
{
if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
return 0;
if (bc->next_event == KTIME_MAX)
return 0;
return bc->bound_on == cpu ? -EBUSY : 0;
}
static void broadcast_shutdown_local(struct clock_event_device *bc,
struct clock_event_device *dev)
{
/*
* For hrtimer based broadcasting we cannot shutdown the cpu
* local device if our own event is the first one to expire or
* if we own the broadcast timer.
*/
if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
if (broadcast_needs_cpu(bc, smp_processor_id()))
return;
if (dev->next_event < bc->next_event)
return;
}
clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
}
static int ___tick_broadcast_oneshot_control(enum tick_broadcast_state state,
struct tick_device *td,
int cpu)
{
struct clock_event_device *bc, *dev = td->evtdev;
int ret = 0;
ktime_t now;
raw_spin_lock(&tick_broadcast_lock);
bc = tick_broadcast_device.evtdev;
if (state == TICK_BROADCAST_ENTER) {
/*
* If the current CPU owns the hrtimer broadcast
* mechanism, it cannot go deep idle and we do not add
* the CPU to the broadcast mask. We don't have to go
* through the EXIT path as the local timer is not
* shutdown.
*/
ret = broadcast_needs_cpu(bc, cpu);
if (ret)
goto out;
/*
* If the broadcast device is in periodic mode, we
* return.
*/
if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
/* If it is a hrtimer based broadcast, return busy */
if (bc->features & CLOCK_EVT_FEAT_HRTIMER)
ret = -EBUSY;
goto out;
}
if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
/* Conditionally shut down the local timer. */
broadcast_shutdown_local(bc, dev);
/*
* We only reprogram the broadcast timer if we
* did not mark ourself in the force mask and
* if the cpu local event is earlier than the
* broadcast event. If the current CPU is in
* the force mask, then we are going to be
* woken by the IPI right away; we return
* busy, so the CPU does not try to go deep
* idle.
*/
if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
ret = -EBUSY;
} else if (dev->next_event < bc->next_event) {
tick_broadcast_set_event(bc, cpu, dev->next_event);
/*
* In case of hrtimer broadcasts the
* programming might have moved the
* timer to this cpu. If yes, remove
* us from the broadcast mask and
* return busy.
*/
ret = broadcast_needs_cpu(bc, cpu);
if (ret) {
cpumask_clear_cpu(cpu,
tick_broadcast_oneshot_mask);
}
}
}
} else {
if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
/*
* The cpu which was handling the broadcast
* timer marked this cpu in the broadcast
* pending mask and fired the broadcast
* IPI. So we are going to handle the expired
* event anyway via the broadcast IPI
* handler. No need to reprogram the timer
* with an already expired event.
*/
if (cpumask_test_and_clear_cpu(cpu,
tick_broadcast_pending_mask))
goto out;
/*
* Bail out if there is no next event.
*/
if (dev->next_event == KTIME_MAX)
goto out;
/*
* If the pending bit is not set, then we are
* either the CPU handling the broadcast
* interrupt or we got woken by something else.
*
* We are no longer in the broadcast mask, so
* if the cpu local expiry time is already
* reached, we would reprogram the cpu local
* timer with an already expired event.
*
* This can lead to a ping-pong when we return
* to idle and therefore rearm the broadcast
* timer before the cpu local timer was able
* to fire. This happens because the forced
* reprogramming makes sure that the event
* will happen in the future and depending on
* the min_delta setting this might be far
* enough out that the ping-pong starts.
*
* If the cpu local next_event has expired
* then we know that the broadcast timer
* next_event has expired as well and
* broadcast is about to be handled. So we
* avoid reprogramming and enforce that the
* broadcast handler, which did not run yet,
* will invoke the cpu local handler.
*
* We cannot call the handler directly from
* here, because we might be in a NOHZ phase
* and we did not go through the irq_enter()
* nohz fixups.
*/
now = ktime_get();
if (dev->next_event <= now) {
cpumask_set_cpu(cpu, tick_broadcast_force_mask);
goto out;
}
/*
* We got woken by something else. Reprogram
* the cpu local timer device.
*/
tick_program_event(dev->next_event, 1);
}
}
out:
raw_spin_unlock(&tick_broadcast_lock);
return ret;
}
static int tick_oneshot_wakeup_control(enum tick_broadcast_state state,
struct tick_device *td,
int cpu)
{
struct clock_event_device *dev, *wd;
dev = td->evtdev;
if (td->mode != TICKDEV_MODE_ONESHOT)
return -EINVAL;
wd = tick_get_oneshot_wakeup_device(cpu);
if (!wd)
return -ENODEV;
switch (state) {
case TICK_BROADCAST_ENTER:
clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
clockevents_switch_state(wd, CLOCK_EVT_STATE_ONESHOT);
clockevents_program_event(wd, dev->next_event, 1);
break;
case TICK_BROADCAST_EXIT:
/* We may have transitioned to oneshot mode while idle */
if (clockevent_get_state(wd) != CLOCK_EVT_STATE_ONESHOT)
return -ENODEV;
}
return 0;
}
int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
{
struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
int cpu = smp_processor_id();
if (!tick_oneshot_wakeup_control(state, td, cpu))
return 0;
if (tick_broadcast_device.evtdev)
return ___tick_broadcast_oneshot_control(state, td, cpu);
/*
* If there is no broadcast or wakeup device, tell the caller not
* to go into deep idle.
*/
return -EBUSY;
}
/*
* Reset the one shot broadcast for a cpu
*
* Called with tick_broadcast_lock held
*/
static void tick_broadcast_clear_oneshot(int cpu)
{
cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
}
static void tick_broadcast_init_next_event(struct cpumask *mask,
ktime_t expires)
{
struct tick_device *td;
int cpu;
for_each_cpu(cpu, mask) {
td = &per_cpu(tick_cpu_device, cpu);
if (td->evtdev)
td->evtdev->next_event = expires;
}
}
static inline ktime_t tick_get_next_period(void)
{
ktime_t next;
/*
* Protect against concurrent updates (store /load tearing on
* 32bit). It does not matter if the time is already in the
* past. The broadcast device which is about to be programmed will
* fire in any case.
*/
raw_spin_lock(&jiffies_lock);
next = tick_next_period;
raw_spin_unlock(&jiffies_lock);
return next;
}
/**
* tick_broadcast_setup_oneshot - setup the broadcast device
*/
static void tick_broadcast_setup_oneshot(struct clock_event_device *bc,
bool from_periodic)
{
int cpu = smp_processor_id();
ktime_t nexttick = 0;
if (!bc)
return;
/*
* When the broadcast device was switched to oneshot by the first
* CPU handling the NOHZ change, the other CPUs will reach this
* code via hrtimer_run_queues() -> tick_check_oneshot_change()
* too. Set up the broadcast device only once!
*/
if (bc->event_handler == tick_handle_oneshot_broadcast) {
/*
* The CPU which switched from periodic to oneshot mode
* set the broadcast oneshot bit for all other CPUs which
* are in the general (periodic) broadcast mask to ensure
* that CPUs which wait for the periodic broadcast are
* woken up.
*
* Clear the bit for the local CPU as the set bit would
* prevent the first tick_broadcast_enter() after this CPU
* switched to oneshot state to program the broadcast
* device.
*
* This code can also be reached via tick_broadcast_control(),
* but this cannot avoid the tick_broadcast_clear_oneshot()
* as that would break the periodic to oneshot transition of
* secondary CPUs. But that's harmless as the below only
* clears already cleared bits.
*/
tick_broadcast_clear_oneshot(cpu);
return;
}
bc->event_handler = tick_handle_oneshot_broadcast;
bc->next_event = KTIME_MAX;
/*
* When the tick mode is switched from periodic to oneshot it must
* be ensured that CPUs which are waiting for periodic broadcast
* get their wake-up at the next tick. This is achieved by ORing
* tick_broadcast_mask into tick_broadcast_oneshot_mask.
*
* For other callers, e.g. broadcast device replacement,
* tick_broadcast_oneshot_mask must not be touched as this would
* set bits for CPUs which are already NOHZ, but not idle. Their
* next tick_broadcast_enter() would observe the bit set and fail
* to update the expiry time and the broadcast event device.
*/
if (from_periodic) {
cpumask_copy(tmpmask, tick_broadcast_mask);
/* Remove the local CPU as it is obviously not idle */
cpumask_clear_cpu(cpu, tmpmask);
cpumask_or(tick_broadcast_oneshot_mask, tick_broadcast_oneshot_mask, tmpmask);
/*
* Ensure that the oneshot broadcast handler will wake the
* CPUs which are still waiting for periodic broadcast.
*/
nexttick = tick_get_next_period();
tick_broadcast_init_next_event(tmpmask, nexttick);
/*
* If the underlying broadcast clock event device is
* already in oneshot state, then there is nothing to do.
* The device was already armed for the next tick
* in tick_handle_broadcast_periodic()
*/
if (clockevent_state_oneshot(bc))
return;
}
/*
* When switching from periodic to oneshot mode arm the broadcast
* device for the next tick.
*
* If the broadcast device has been replaced in oneshot mode and
* the oneshot broadcast mask is not empty, then arm it to expire
* immediately in order to reevaluate the next expiring timer.
* @nexttick is 0 and therefore in the past which will cause the
* clockevent code to force an event.
*
* For both cases the programming can be avoided when the oneshot
* broadcast mask is empty.
*
* tick_broadcast_set_event() implicitly switches the broadcast
* device to oneshot state.
*/
if (!cpumask_empty(tick_broadcast_oneshot_mask))
tick_broadcast_set_event(bc, cpu, nexttick);
}
/*
* Select oneshot operating mode for the broadcast device
*/
void tick_broadcast_switch_to_oneshot(void)
{
struct clock_event_device *bc;
enum tick_device_mode oldmode;
unsigned long flags;
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
oldmode = tick_broadcast_device.mode;
tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
bc = tick_broadcast_device.evtdev;
if (bc)
tick_broadcast_setup_oneshot(bc, oldmode == TICKDEV_MODE_PERIODIC);
raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}
#ifdef CONFIG_HOTPLUG_CPU
void hotplug_cpu__broadcast_tick_pull(int deadcpu)
{
struct clock_event_device *bc;
unsigned long flags;
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
bc = tick_broadcast_device.evtdev;
if (bc && broadcast_needs_cpu(bc, deadcpu)) {
/*
* If the broadcast force bit of the current CPU is set,
* then the current CPU has not yet reprogrammed the local
* timer device to avoid a ping-pong race. See
* ___tick_broadcast_oneshot_control().
*
* If the broadcast device is hrtimer based then
* programming the broadcast event below does not have any
* effect because the local clockevent device is not
* running and not programmed because the broadcast event
* is not earlier than the pending event of the local clock
* event device. As a consequence all CPUs waiting for a
* broadcast event are stuck forever.
*
* Detect this condition and reprogram the cpu local timer
* device to avoid the starvation.
*/
if (tick_check_broadcast_expired()) {
struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
cpumask_clear_cpu(smp_processor_id(), tick_broadcast_force_mask);
tick_program_event(td->evtdev->next_event, 1);
}
/* This moves the broadcast assignment to this CPU: */
clockevents_program_event(bc, bc->next_event, 1);
}
raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}
/*
* Remove a dying CPU from broadcasting
*/
static void tick_broadcast_oneshot_offline(unsigned int cpu)
{
if (tick_get_oneshot_wakeup_device(cpu))
tick_set_oneshot_wakeup_device(NULL, cpu);
/*
* Clear the broadcast masks for the dead cpu, but do not stop
* the broadcast device!
*/
cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
}
#endif
/*
* Check, whether the broadcast device is in one shot mode
*/
int tick_broadcast_oneshot_active(void)
{
return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
}
/*
* Check whether the broadcast device supports oneshot.
*/
bool tick_broadcast_oneshot_available(void)
{
struct clock_event_device *bc = tick_broadcast_device.evtdev;
return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
}
#else
int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
{
struct clock_event_device *bc = tick_broadcast_device.evtdev;
if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
return -EBUSY;
return 0;
}
#endif
void __init tick_broadcast_init(void)
{
zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
#ifdef CONFIG_TICK_ONESHOT
zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);
#endif
}
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